Rock drill



Feb. l5, 1949. J. c. c URTls ETAL Rocx DRILL Filed July 1, 1945 f.0..Z m ewa m d m M, A n w ,3 w/ M 7 J. C. CURTIS FAL ROCK DRILL 3 sheets-sheet s I Filed July 1, 1945 `Patented Fel). 15, 194g.

iiiszs RocK DRILL .lohn C. Curtis and Elmer N. H., assignors to Joy G. Gartin, Claremont, Manufacturing Company, a corporation of Pennsylvania Application July 1, 1943, Serial No. 493,086

13 Claims.

This invention relates to rock drills and more particularly to improvements in a hammer rock drill of the stoper type.

An object of the present invention is to provide an improved rock drill. Another object is to provide an improved stoper rock drill having im proved feeding means and improved feed controlling means. Still another Objectis to provide j an improved stoper rock drill having a novel supporting handle arrangement. A further object is to provide an improved controlling means for a rock drill. A still further object is to provide an improved throttle valve mechanism having an improved throttle valve and handle construction whereby operation of the throttle valve is facilitated. A still further object is to provide an im- 'proved drill supporting handle having an im-V proved feed control valve associated therewith. Still another object is to provide an improved control valve mechanism for a stoper rock drill for controlling the flow of pressure fluid to the hammer motor, to the feeding means and to the drill lubricating means. Still another object is to provide an improved rock drill having novel coi binations and arrangements of parts. These and other objects and advantages of the` invention will, however, hereinafter more fully appear.

In the accompanying drawings there is shown for purposes of illustration one form which the invention may assume in practice.

In these drawings:

Fig. 1 is an elevational view of a stoper rock drill constructed in accordance with an illustrative embodiment of the invention, the `forward portion of the drill being broken away to facilitate illustration.

Fig. 2 is a vertical sectional view, with parts in side elevation, taken substantially on line 2-2 of Fig. 1.

Fig. 3 is an enlarged fragmentary sectional view taken on the plane of Fig. 2, showing details of the throttle valve mechanism and the automatic lubricator.

Fig. 4 is a horizontal sectional view taken subving the valve in a different position.

Fig. l0 is a horizontal sectional viewvtaken substantially on line Ill-I 0 of Fig. 3.

Fig. 11 is a detail vertical sectional view taken on line l l,-H ofFig. 10. l

Fig. 12 is a detail horizontal sectional view taken substantially on line |2-l2 of Fig. 3. A,

Fig. 13 is a detail sectional horizontal view taken substantially on line |3443 of Fig. 3.

Fig. 14 is an enlarged detail vertical sectional view taken substantially on line M l of Fig. l.

Fig. 15 is a detail horizontal sectional view taken on line l5|5 of Fig. 14.

Fig. 16 is a cross sectional view, through the drill, showing the novel handle arrangement.

In this illustrative embodiment of the invention, there is showna stoper rock drill, generally designated l, generally ycomprising a pneumatic feeding means 2, an automatic lubrcator 3, a throttle valve mechanism 4, and a supporting handle 5 carrying a feed control valve mechanism 6. The pressure fluid motor for percussively actuating and rotating the drill steel is supported and fed by the feeding means 2 and herein may be similar to that disclosed in our copending'appli- .cation,.Serial No. 475,782, filed February 13, 1943.

While the ro'ck drill disclosed is of the st oper type, it will be evident that features ofthe invention may be embodied in other types of rock drills.V

The hammer motor is generally designated l, and, herein for illustrative purposes, is shown to comprise Va cylinder 8 having a bore 9 containing a reciprocatory hammer piston l0 (see FigjZ). Associated with the hammer piston is a rifle bar i I of a conventional ratchet and pawl mechanism for imparting intermittent rotary motion to the piston, and the rotary motion of the piston vis transmitted to the drill steel through transmission connections fully described in the copending application above referred to. Rotation of the hammer piston may be interrupted at will during running of the motor by means of a rotation release ring operated by pressure fluid in the manner fullyv disclosed in the John C. Curtis Patent No. 2,251,269, granted August 5, 1941. .The throttle valve mechanism 4 of thfdrill controls the flow of pressure iiuid to the hammer motor and the rotation release'ring, and thefhammer motor includes a conventional distributing valve mechanism I2 for controlling the distribution rof rpressure iiuid to the motor cylinder. `The strucis arranged in the bore.

tion mechanism and the rotation release do not per se enter into the present invention, further description and illustration thereof are herein unnecessary.

The supporting handle 5 projects laterally from one side of the hammer motor cylinder 8 and is so arranged that handling and supporting of the drill are facilitated. `This handle has its inner end tapered at I3 to fit a conical bore i4 formed in the cylinder wall and is held in position by Va screw plug I5 threaded at i6 within a boss projecting from the cylinder. A split ring VI isv arranged in an annular groove n the handle periphery, and the screw plug. I engages this ring to hold the handle tightly in position. rThe hanz dle has at its outer extremity a grasping portion I8 adapted to be grasped by one hand of the operator, and the feed control valve mechanism t is associated with this grasping portion in a man# ner to be later explained. Attached as by side l bolts I9 to the rear end ofthemotor cylinder is av rear head block 2t which carries the throttle valve mechanism 4 and the automatic lubricator 3. The pneumatic feeding 'means 2 comprises a tubular feed cylinder 2|- axially alined with the hammer motor cylinder and having'a front annular ange'22 clamped against a shoulder 23 on a rear head member 24 of the hammer motor. A cylindrical sleeve 25 has a front annular flange 26 abutting the flange 22, and the rearward por-v tion of the feed cylinder extends through and 'fits the bore of this sleeve in the manner clearly shown in Fig. 3. The feed cylinder and sleeve 25 have their flanges clamped tightly against the.

rear head member 2A of the hammer motor by an inner flange 21 on the rear head block 2Q,

' abutting the sleeve flange V25 in the manner shown.

Contained in the feed cylinder 2l is a feed piston f28 having its piston rod 29 extending rearwardly through a bushing 39 fitted in a sleeve 3l secured Within the rear end portion of the feed cylinder 2! as shown in Fig. 2. Attached to the rear end rof the'feed piston rod is an abutment engaging point 32 adapted to engage an extraneous abutl-ment.

AArranged with its axis lying in a longitudinal plane at right angles of a plane including the longitudinal axis of the supporting handle 5 is a rotary grasping handle 33 of the throttle valve mechanism 4. This handle is preferably of tubu- *lar form and is corrugated or longitudinally ribbed on its exterior to facilitate gripping thereof. VThe handle is journaledV at its ends respectively in a front bracket 34 integral with the motor cylinder and upon a rear boss 35 integral with the rear head block 23. The Vfront bracket has a bore 36 receiving a bushing 3l in which a reduced stem 38 on the handle is journaled. Axially alined with the handle is a bore 39 in a valve casing 40 integral with the head block 2Q, and a rotary throttle valve 4I of cylindric form The throttle valve has a valve stem 42, generally square in cross section, slidingly iitted in a square recess B3 in the valve handle 33 so that the valve is connected to the handle for rotation thereby. Attached at it to the rear head block is a. conventional hose connection for supplying fluid under pressure to the hollow interior 45 of the throttle valve, and

the iiuid flowing to the valve acts on thelower end of the. valve to force the latter upwardly within the valve bore. To oppose the pressure of 'the fluid acting on the lower end of the 'throttle valve, there is provided a packed piston 4l' attachedby `a screw 48 to the valve and'fitting a Fig. 2).

35. To absorb the axial upward thrust of the Valve handle 33, there is provided an end-thrust bearing .5I engaging a thrust washer 52 seated against the upper wall of the bracket bore 3B (see Due to the provision of the opposing pressures at the opposite ends of the valve, rotation of the valve is relatively easy.

As shown most clearly in Fig. 16, the handles I8 and 33 lie in longitudinal planes disposed at right angles with respect to each other with the axes of the handles lying in a longitudinalplane disposed wholly outside of the body of the drill. Thusthe handles are both located at the same side of a longitudinal plane passingthrough-'the axis of the drill body. By such an arrangement of the handles, it is possible to locate the drill close to a corner without affecting the proper handling and control of the drill.

The automatic lubricatorff is 'designed .to supply lubricant to the throttle valve bore andi-to the moving parts of the drill hammer motor. This lubricator forV illustrative purposes` is shown to comprise an annular` lubricant reservoir formed in the head block 2S and surrounding the sleevet, and having a conventionalller plug as shown in Fig. i. Thelower part of thehead block: tightly fits at El the cylindricexterior of the sleeve 25 to prevent leakage of lubricant. There is an annular groove 53 intheblock closely Surrounding the sleeve 25 and .connected through a restricted annular spacey 59 with .the reservoir. A passage communicates with this groove and is connected to a passage 5I (see Fig. lil) leading to the throttle valve receiving bore 39 A and a branch passage B2 which extends longitudinally of the motor cylinder and is connected to ducts leading to the various surfaces ofthe motor to be lubricated, in a well lmown'manner. As shown in Fig. l0, a passage 63 connects the throttle valve receiving bore 39 to the upper part of the lubricant reservoir 55.50 that fluid under pressure may be admitted to the reservoiry during running of the drill to act on the upperl surlaceof the lubricant to force the lubricant .through .the passages 55h-Ei and 62'to the various partsto be lubricated.

New referring to the speciiic structureof the throttle valve mechanism 6., it will' be noted` that the throttle valve M has a port i513 (seeFigsfB i3) for connecting the valve interior. 4-6 With a chamber 55 communicating withrthe inletpassage S5- of the hammer motor. The throttle valve has a port '5l' (Fig. 4l) for connecting the hollow interior e6 of the throttle rvalve with acirthe control valve mechanism 6 with a passage 'i3 communicating with a passage ld, lthelatter in turn communicating with a passage `'I5 in the rear head member 24. The passage `15 leads to the uppei` end of the feed cylinder 2| at the upper side of the feed piston. rlhe specific structure of the feed control valve mechanism will be later explained.

As shown in Fig. 10, the throttle valve has a port communicating with a peripheral groove `'I8 on the valve, and this groove vis communicable with the passage E3 leading to the upper side of the lubricant reservoir. When the groove 'i8 is in communication with the passage S3, .fluid under Ipressure may ow from the interior of the throttle valve to the reservoir. Extending longitudinally along the exterior periphery of the throttle valve are shallow lubricant grooves '|52 and 8!) communicating at their upper ends with an annular groove 8|, and lubricant may iiow through these grooves to lubricate the walls of the valve receiving bore in an obvious manner. The groove 8|) communicates with a peripheral groove 82 which is communicable with the motor inlet passage S5. This enables the reservoir to be connected to atmosphere through the motor exhaust whenever the drill hammer motor is vnot running. As shown in Fig. 12, rotary movement of the throttle valve 4| is limited by a spring pressed detent element 83 projecting Within a peripheral groove 84 on the valve. 'A screw plug 85 holds the spring -86 under compression and is removable to attain access to the parts. This detent element also serves to hold the throttle valve in its different positionsof adjustment.

The feed control valve mechanism 6 will now be described in detail. As shown in Figs. l and 5, the supporting handle 5 has at its outer end a conical bore 9|) which receives a conical feed control valve 9|. This valve is rotatably mounted in the bore and has a stem 92 arranged in a bore 93 extending longitudinally through the grasping portion i8 of the handle 5. Secured to the lower end of the valve stem S2 is a lrnoblike handle 84 conveniently arranged in adjacency to the grasping portion i8 so vthat the operator may readily control the feed without removing his hand from thesupporting handle. The valve is held in its adjusted position by a serrated plate 95 yieldingly held in engagement with a plug S6 by a coil spring 9! acting on the plate. This plate is connected for rotation' with the valve by a square stem 923 thereon slidingly fitted in a square bore 99 in the valve. A pin V||l| projects into a circumferential slot l d2 on the valve (Figs. 8 and 9) for limiting rotary valve movement. The uid supply passage |2 in the handle 5 communicates with a bore |53 at the 'upper side of the valve, and the valve body has a passage |04 therethrough for connecting the bore |53 with the feed passage 1'53. The valve has a peripheral V-notch m5 communicating with the passage |84 so that graduated ow of fluid may be attained. A vent passage |06 connects the valve receiving bore 9G to atmosphere, and the valve is traversed by a passage H31 for connecting the feed passage i3 to the vent passage Ulli. Thus the ilow of pressure fluid from the throttle valve to the feed cylinder may be regulated as desired, and when the fluid supply to the feed is cut olf by said control valve, the feed cylinder may be vented, thereby to attain an extremely sensitive control of the feed.

Rotation release is controlled by a valve ||0 rotatably mounted in a bore Il in the head block 2B (Fig. 13). The valve has a handle I I2 and has a passage 3 for connecting the fluid chamber 65 to a passage I4 leading to the rotation release ring in the manner fully disclosed in theCurtis |00 on a screw plug Ashut down the flow patent above referred to. Communicating with the valve receiving bore Il is a vent passage H5, and the valve is traversed by a passage H6 for connecting the passage IM to this vent passage. It is accordingly evident that the rotation release ring may be either supplied with fluid or vented to atmosphere under theV control of the valve H0.

The general mode of operation of the improved rock drill is as follows: The rock drill may be suitably positioned and supported with respect to the work by the operator grasping the supporting handle 5 in one hand and the throttle valve handlet in the other hand. When the drill is in upright drilling position, the operator may turnthe throttle valve handle 33 to rotate the throttle valve 4| into a position wherein the port 64 communicates with the chamber 65, thereby to admit pressure fluid from the supply Yhose through the valve interior to the motor inlet passage Se, to eect running of the motor. During running of the hammermotor, pressure fluid may flow through port 11, groove 'I8 and passage 63 to the upper side of the lubricant reservoir so that pressure fluid acting on the surface of the lubricant forces the lubricant through groove 58, passages S0, 6| and 62 to the parts of the drill to be lubricated. The passage 6| supplies lubricant to the throttle valve while the passage 62 supplies lubricant to the moving motor parts. Concurrently pressure uid may flow through port 61, groove 68, passages 69, 10, 7|, '|2, to the bore |03 and through the passage Idd in the feed control valve 9| to passages 13, 'I4 and 15 leading to the feed cylinder to effect movement of the feed cylinder with respect to the feed piston to feed the drill hammer motor toward the work. The flow of pressure fluid to the feed cylinder may be regulated by the control valve 3| and in the event it is desired to stop suddenly the feed, the valve 9| may be turned into a position to effect venting of the feed cylinder to atmosphere through vent passage ile. Whenever the throttle valve il is rotated into a position to hammer motor, the lubricant reservoir is vented 'through passage 63, groove S0, groove 82, motor inlet passage S6 and the motor exhaust. Thus lubricant flow ceases when the drill is not running. Rotation of the drill steel may be interrupted at will during running of the motor simply by turning the control valve ||U into a position to supply pressure fluid from the chamber 65 to the passage H4 leading to the rotation releasering. By the novel arrangement of the handles 33 and 5 the drill may be readily positioned and supported with and the throttle valve 4| and the feed control valve 9| may be readily adjustediwithout the operator removing his grasp on the handles. After the drill is started to run by turning on the throttle valve, feed may be controlled entirely by the feed control valve. By the provision of the valve-piston 41 in the bore 49 of the throttle valve handle 33, the pressure acting on the lower end of the throttle valve is to a substantial extent counterbalanced so that the valve may be easily turned and at the same time the throttle valve handle'is held upwardly in position against its upper bearing. The novel arrangement of the automatic lubricator with respect to the feed cylinder results in a drill structure which is extremely compact. :vantages 1 ent to-those skilled in the art.

of pressure fluid to the'drillV respect to the work,

While there is in this application specifically ldescribed one form which the invention may assume in practice, ity Will be understood that this formof the same is shown for purposes of illustration andv that the invention may be modified and embodiedy in various other forms Without -departing from its spi-rit or the scope of the appended claims.

What We claim as new and desire to secure by Letters Patent is:

1. In a rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feeding means therefor, a pair of lever arms projecting laterally from the side of the drill and disposed at a substantial angle with respect to each other, with the drill arranged at least substantially at the apex of the angle,v a throttle valve mechanismfor controlling fluid vflow to said motor including a throttle valve having a control handle carried by one of said lever arms, and feed control means for controllingy uid flow relative to said feeding means including a feed control valve having a control handle carried by said other lever arm, said handles being disposed in fixed spaced relation and 4having grasping portions at all times eX- .tending in parallelism longitudinally of the drill.

2. In a rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feeding means therefor, a pair of lever arms projecting laterally from the side of the drill and disposed at a substantial angle with respect to each other, with the drill arranged at least substantially at the apex of the angle, one of said lever arms carrying a drill supporting handle, a throttle valve mechanism for controlling uid flow to said motor including a throttle valve having a control handle carried by one of said lever arms, and feed control means for controlling fluid flovv relative to said feeding means including a feed control valve having a control handle carried by said other lever arm, all three of said handles having their grasping portions extending longitudinally of the drill always in parallelism and in iixed spaced relation to the "l' longitudinal axis of the drill.

3. In a rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feedingmeans therefor, apair of lever arms I. projecting laterally from the side of the drill and disposed at a substantial angle with respect to each other, with the drill arranged at least substantially at the apex of the angle, one of said lever arms carrying a drill supporting handle, a throttle valve mechanism for controlling fluid flow to said motor including a throttle valve having a control handle carried by one of said lever arms, and feed control means for controlling fluid flow relative to said feeding means including a feed control valve having a control handle carried by said other lever arm, all three of said handles having their grasping portions `extending longitudinally of the drill always in parallelism and in fixed spaced relation to the longitudinal axis of the drill, and said handle for said feed control valve being arranged in juxtaposition to said drill supporting handle whereby the feed may be controlled and the drill may be supported with but one hand of the operator. i

4. In a rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feeding means therefor, a pair of lever arms projecting laterally from the side of the drill and disposed at a substantialangle with respectto each` other, with the dri-ll arrangedat least substantially at theapex of the angle, one of said arms carrying, a drill supporting handle, and control valve means including aA control valve having an operating; handle carried by said other lever arm, the axes of said handlesdisposed in fixed spaced relation with respect to the longitudinal axis of the drill and respectivelyflyingA inlongitudinal planes including the longitudinal axes of said lever. arms,

5. In` a rock drill, the combination comprising a fluid actuated steell .actuating motor, uidactuated feeding means therefor; a kpair ofl lever arms projecting laterally from` the side; of the drilland disposed at. a substantial; angle with respect to each other, with the drill arrangedA at least substantiallyy at the apex of the angle, one of said arms carrying a drill supporting handle, and control valve means includ-ing a controlv valve having an operating handlecarried.y by saidother lever arm, the axes of said handles disposed in fixed spaced:V relation with respect to the longii tudinal axis oft-he drill and respectively. lying longitudinal planes including the longitudinal axes of said lever arms, and! said: control' valve means also including a control valve arranged at the outer extremity of said lever arm which carries. the drill supporting handle.

6. Ln a rock drill, the combination compris-V` ing a steel actuating motor, feeding means there'- for, a pair of lever arms projecting laterally from the 'side ofthe drill ariddisposedV at a substantial angle with respect to. each other, with the drill arranged at least substantially at the apex: of the angle, and controlling' means for said motor and'sald feeding mear-is including control valves having control handles carried at the outer extremities of said lever arms re'- spectively and extending longitudinally of the drill in fixed spaced relation in all positionsV of said valves, one handle for the motor control valve and the other for said feed control valve, and said handles adapted to be grasped by the operator, one in each. handiwhereby the drill may ce positioned and supported with respect to the Work. Y

7, ln a stoper rock drill, the combination comfprising a fluid actuated steel 'actuatingmoton fluid actuated feeding means for said motor airanged in axial alinenient therewith, a drill Vsupporting handle secured to andl disposed laterally of the drill, and control valve means including a control valve having an operating handle dis-V posed laterally of the drill, said handles arranged in fixed relation, and the axes of said handles respectively lying in planes extending longitudinally cf the drill and disposed at a substantial angle with respectto each other and with said handle axes both wholly at one side of a longitudinal plane including the longitudinal asis of the drill. f

8. in a stoper rochv drill, the combination coni'- prising a fluid actuated steel actuating motor, ilu-id actuated feeding means for said motor arranged in axial alinement therewith, a drill supporting handle secured toand disposed lat erally of the drill, and control valve means for the drill having a control valve operating handle disposed laterally of the drill at a, substantial angle with respect to said supporting hancile, saidl handles having* grasping', portionsV spaced atv substantial distances laterally from the drill axis and disposed in fixed relation both at'one side of a vertical plane including the longitudinal axis of the drill',

9. In a stoper rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feeding means for said motor arranged in axial alinement therewith, a drill supporting handle secured to and disposed laterally of the body of the drill, and control valve means for the drill having a control valve operating handle disposed laterally of the body of the drill at a substantial angle with respect to said supporting handle, said handles disposed in xed relation with respect to the drill body and having grasping portions spaced at substantial distances laterally from the drill axis with the axes of said grasping portions lying in a longitudinal vertical plane located wholly outside of the body of the drill.

10. In a rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feeding means therefor, a throttle valve mechanism for controlling fluid flow to said motor including a throttle valve having a control handle, and feed control means for controlling iiuid ow to said feeding means including a feed control valve having a control handle, said handles being disposed with their axes in fixed spaced relation and lying in angularly related longitudinal planes both at one side of a longitudinal plane including the longitudinal axis of the drill, and said handles having grasping portions, one adapted to be gripped in the palm of each hand of the operator whereby the drill may be readily supported and controlled.

11. In a rock drill, the combination comprising a uid actuated steel actuating motor, fluid actuated feeding means for said motor, lever arms projecting laterally from the sides of the drill and disposed at a substantial angle with respect to each other, a throttle valve mechanism for controlling fluid flow to said motor and including a throttle valve carried at the outer eX- tremity of one of said lever arms and having a control handle, and feed control means for controlling nuid flow to said feeding means including a feed control valve carried at the outer extremity of the other lever arm and having a control handle, said handles being disposed with their axes in xed spaced relation and in parallelism, said handles extending longitudinally of the drill and both being located wholly at one side of a longitudinal plane including the longitudinal axis of the drill, and said handles having grasping portions, one adapted to be gripped in each hand of the operator whereby the drill may be readily supported and controlled, and said lever arms being so arranged with the drill at least substantially at the apex of the angle of the drill at the opposite side of said longitudinal plane may be placed close to a corner. K

12. In a rock drill, the combination comprising a fluid actuated steel actuating motor, fluid actuated feeding means for said motor, lever arms projecting laterally from the side of the drill in right angular relation both at one side 10 of a longitudinal plane including the longitudinal axis of the drill thereby leaving the opposite side of the drill free and clear, a throttle valve mechanism for controlling Huid flow to said motor including a throttle valve having a control handle carried at the outer extremity of one lever arm, and feed control means for controlling uid flow to said feeding means including a feed control valve having a controlhandle carried at the outer extremity of the other lever arm, said handles being disposed with their axes in fixed spaced relation and in parallelism and extending longitudinally of the drill, and said handles having grasping portions, one adapted to be grasped in each hand of the operator whereby the drill may be lreadily supported and controlled.

13. In a stoperrock drill, the combination comprising a uid actuated steel actuating motor,

,s fluid actuated feeding means secured to said motor for feeding the drill steel toward the work as the steel is percussively actuated, and a pair of lever arms projecting laterally from the side of the drill in right angular relation to the longitudinal axis of the drill, said lever arms disposed in il-relation at a substantial to each other, with the drill arranged at least substantially at the apex of the angle, said lever arms carrying handles at their outer extremities, said handles at all times extending longitudinally in parallelism and in fixed spaced relation to the longitudinal axis of the drill, one adapted to be grasped in each hand of the drill operator whereby the drill may be positioned and supported with respect to the work, and said lever arms being so arranged that the drill may be placed close to a corner with the drill operator stationed at the side of the drill opposite from the apex.

JOI-IN C. CURTIS. ELMEZE'l G. GARTIN.

REFERENCES CITED le of this patent:

UNITED STATES PATENTS Number Name Date 1,020,619 OBrienV Mar. 19, 1912 1,172,238 Gilman Feb. 15, 1916 1,302,752 Adams May 6, 1919 1,570,954 Hansen Jan. 26, 1926 1,574,768 Tuttle Mar. 2, 1926 1,651,199 Gartin Nov. 29, 1927 1,679,138 Osgood July 31, 1923 1,774,186 Rundqvist Aug, 26, 1930 1,796,667 Rundqvist Mar. 17, 1931 1,850,565 O-Farrell Mar. 22, 1932 1,923,797 Richardson Aug. 22, 1934 1,956,644 Hamerly May 1, 1934 2,296,817 Gartin Sept. 22, 1942 2,312,941 Tucker Mar. 2, 1942 2,318,593 Curtis May 11, 1943 angle with respect 

